openrisc: fix arbitrary kernel memory access via or1k_atomic syscallgrafted

sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user
pointers, v1 and v2, and swaps the words they point to in hand-written
assembly.

    l.lwz   r29,0(r4)
    l.lwz   r27,0(r5)
    l.sw    0(r4),r27
    l.sw    0(r5),r29

The pointers are not checked with access_ok(). The four memory
accesses also have no exception table entries.

A caller passes a kernel address as either pointer, and the syscall
reads from and writes to it directly.

This gives an unprivileged process a kernel read/write primitive. It
overwrites kernel data such as the sys_call_table, gaining code
execution in kernel context.

Check both pointers before entering the critical section. Add fixups
for the four memory accesses so faults on valid but unmapped user
addresses return -EFAULT.

[shorne@gmail.com: fix comment style]
Fixes: 9d02a4283e9c ("OpenRISC: Boot code")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Stafford Horne <shorne@gmail.com>

1 files changed, 56 insertions, 0 deletions

diff --git a/include/net/psample.h b/include/net/psample.h
new file mode 100644
index 000000000..5071b5fc2
--- /dev/null
+++ b/include/net/psample.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_PSAMPLE_H
+#define __NET_PSAMPLE_H
+
+#include <uapi/linux/psample.h>
+#include <linux/list.h>
+
+struct psample_group {
+	struct list_head list;
+	struct net *net;
+	u32 group_num;
+	u32 refcount;
+	u32 seq;
+	struct rcu_head rcu;
+};
+
+struct psample_metadata {
+	u32 trunc_size;
+	int in_ifindex;
+	int out_ifindex;
+	u16 out_tc;
+	u64 out_tc_occ;	/* bytes */
+	u64 latency;	/* nanoseconds */
+	u8 out_tc_valid:1,
+	   out_tc_occ_valid:1,
+	   latency_valid:1,
+	   rate_as_probability:1,
+	   unused:4;
+	const u8 *user_cookie;
+	u32 user_cookie_len;
+};
+
+struct psample_group *psample_group_get(struct net *net, u32 group_num);
+void psample_group_take(struct psample_group *group);
+void psample_group_put(struct psample_group *group);
+
+struct sk_buff;
+
+#if IS_ENABLED(CONFIG_PSAMPLE)
+
+void psample_sample_packet(struct psample_group *group,
+			   const struct sk_buff *skb, u32 sample_rate,
+			   const struct psample_metadata *md);
+
+#else
+
+static inline void psample_sample_packet(struct psample_group *group,
+					 const struct sk_buff *skb,
+					 u32 sample_rate,
+					 const struct psample_metadata *md)
+{
+}
+
+#endif
+
+#endif /* __NET_PSAMPLE_H */